When is it usually safe to start sleeping flat on the back after breast augmentation?

We allow our breast augmentation patients to sleep in whichever position they find most comfortable after their operation.Most women won't feel too comfortable sleeping on their stomach, but sleeping on the back or side is just fine.We also have our breast augmentation patients wear a support bra day and night for a few weeks. 

Thank you for the question.
I would suggest that you run this question by your plastic surgeon given that he/she is ultimately responsible for your care and knows  your situation and the operation performed intimately.
In my practice, most patients are able to sleep on their back within a week and on the sides roughly 2-3 weeks after surgery (with pillow for support as well as supportive bra on).
Best wishes.